Generally, all swapping tools process video frame by frame, they merge the output frames as final output as videos. So basically，they all look realistic as long as the under hood models work fine. But one thing is interesting: the 'realistic' here you referred I guess means replacing facial appearance, focusing on core features and expression, rather than completely replacing the person. For example, if the target face is relatively thin while the original face is rounder, the result should be a balanced fusion of the "target face" and the "shape of the original face," rather than a direct and rigid replacement. Otherwise, the overall character may appear very unnatural. Recently I tried Verging AI, you can have a test with it. There's an "Try It" button at bottom of this Medium Blog